Measuring larger diameter by smaller vernier caliper

Jul 17, 2010 • By • 4,603 Views

In the process of machining, we often have the problems about measuring the outside diameter of some Axis and item like Disc which have larger diameter. In case, we do not have suitable measuring instruments, it is acceptable to adopt the smaller vernier calipers to have indirect measurements. Please find the method as below:


Then simplify the formula and put 2R=D in the formula we get:

b=2h(D-h)       (1)

D= +h     (2)

D is the diameter of the measured item, b is the diameter of the vernier caliper and h is the distance from the measuring point to the main branch of the caliper. In the process of machining, adopting the formula (1), b max and b min value can be made out just put the D max value, D min value and h value into (1). Hereafter, by controlling the b max value and b min value can get the item diameter. If the axis and item like Disc are needed in the process of machining, then the formula (2) is available.

Comparison between Dial caliper and Vernier caliper

Firstly, Dial caliper is 2-3 times expensive than vernier caliper, meanwhile, it less 1/2 and 1/3 than Digital caliper. For the reading speed and reliability, the average measuring time of Dial caliper is 60-75% more than Vernier caliper's. According to the measure value is very clear, so it is hard to appear the reading error.

FEATURES of Vernier Calipers
* Made of stainless steel
* Used for 4-way measurements: outside, inside, depth, step
* High quality basic vernier caliper
* English and metric measurement